Television system



Nov. 27, 1945.

G. E. SLEEPER, JR

TELEVISION SYSTEM Filed Aug. 30, 1943' 3 Sheets-Sheet 1 INVENTOR m m m. m. S E m w G.

U ,N R m n m Nov. 27, 1945. G. E. SLEEPER, JR

TELEVISION SYSTEM Filed Aug. 30, 1943 3 Sheets-Sheet 2 INVENTOR GEORGE E. SLEEPER. JR. flfl. a? W ATTORNEK Nov. 27, 1945. SLEEPER, JR 2,389,64

TELEVISION SYSTEM Filed Aug. 50, 1945 :5 Sheets-Sheet s /T\ l I i 1 l I 87 I a 1 l \J/ 0 XI L I 1 5 +262 L/NE$ Z r ';3 SEC.

9. INVENTOR, RED GE RGE E. SLEEPER. JR.

--------- Y'LLOW BY BLUE .GREEN A TTORNE K Patented Nov. 27, 1945 UNITED STATES PATENT OFFICE TELEVISION SYSTEM George E. Sleeper, Jr., Berkeley, Calif. Application August so, 1943, Serial no. 500,518

12 Claims. (Cl. 178-52) This invention relates to television systems, and in particular to a system for transmitting pictures in color. This application is a continuation in part of my pending application Serial No. 474,787, filed February 5, 1943.

An object of my invention is to provide a television system which will eliminate the principal disadvantages inherent in present systems.

'One such system employs rotating color filter discs in the transmitter and receiver. This involves mechanical difficulties and the problem of synchronization. In my system no mechanically moving parts are used. Systems which require projecting images of successively different colors on the photo-sensitive screen of the pick-up tube do not produce true color pictures because the discharge lag, especially in the storage-type tube, causes a carry-over of one color image to the next, with an undesirable mixing of colors. This objection is overcome in my system by allotting separate areas of the screen to each color, so that each area is always receiving images of the same color. Another system employs a separate tube for each color which has the disadvantages of increased cost and the difficulty of placing the tubes close enough together. My system employs a single tube for pickup and a single tube for picture production.

Another object of my invention is to make it possible to employ a standard black and white television system for transmitting color pictures by the addition of simple parts which effect the conversion. I accomplish this by introducing into the optical system which projects the images onto the screen of the pickup tube, a suitable means for simultaneously producing a plurality of images of the object, filtering each of these images for a different color, and projecting each color image on a separate area of the screen. These images are then scanned in a group as one picture in the same manner as a single black and white picture. I

The tube in the receiver reproduces in black and white separate images corresponding to the color images in the pick-up tube. These images lack only color; they have the correct detail and intensity. The color is restored to each image by collecting it through a color filter and then by. a suitable optical means the color images are superimposed on the viewing screen to produce a picture of the original object in its natural color.

It will be noted that the conversion of a standard television system to color is accomplished simply by adding an optical means at the transmitter which will project a plurality of images of diflerent color into the tube and by adding a similar optical means at the receiver which reverses the process and assembles the picture.

Figure 4 shows another means for this purpose.

Figures 5 to 8 are diagrams illustrating how the lines are arranged in the color fields.

Figure 9 is a key to the color symbols.

Figure 10 is a diagram which illustrates the method of scanning the quadchromatic field.

Figures 11 and 12 illustrate the production of the deflection coil curve.

Figure 13 illustrates the curve produced by the timing pulse generator.

Figure 14 shows a modified circuit for use in an electrostatic deflection system.

The number of color images obtainable by my system is a matter of choice. For purposes of illustration, I have disclosed four. I shall, there-- fore, refer to the lens system which produces the four images as a quadchromatic lens.

Referring to Fig. 1, the object ill is picked up by the quadchromatic lens II, which projects four images I2, l3, It, I5 of different color onto the photoelectric screen iii of the pick-up tube H. The images l2, l3, Ill, l5 may be blue, red, yellow, and green, respectively. The four images are conveniently grouped in a quadrangle. An important feature of my system is that the images do not overlap. The area of the screen It upon which any particular color image is projected continuously receives and responds to images of that same color.

The pick-up tube and transmission equipment may be of the conventional construction employed for black-and-white television and comprises the cathode ray tube ll, operated in the usual manner for developing picture signals and provided with a photo-sensitive mosaic screen it. The electron beam 20 is projected onto the screen I6 and is caused to scan the screen in the usual manner by means of deflection coils 2|, 22, con

nected to line and frame deflection generators 23, 24, respectively. The responses from the photo-sensitive screen are conveyed to the amplifier and radio transmitter 25.

The radio receiver 26 (Fig. 2) is connected to the line and frame deflection generators 21, 28 which are connected to the deflection coils 29, 30,

respectively, which deflect the electron beam 3| of the cathode ray tube 32 in the usual manner. The picture signals supplied to the tube produce four pictures 33, 34, 36, 36, corresponding to the four images l2, I3, l4, l6. These pictures are black-and-white but reproduce the detail and intensities of the originals.

A quadchromatic lens 31 which may be similar to the lens Ii, but reversed, collects the four-pictures, supplies the appropriate color to each by a filter, superimposes the four color images and.

projects a picture in natural color of the object in on the viewing screen 38.

The quadchromatic lenses referred to above could be constructed in diiferent ways. For example, four separate lens systems could be employed, each provided with a filter. Each of these lens systems would project an image of the object in a different color on the screen of the pick-up tube. This means is thought to be readily understood without illustration.

An alternative means is shown in Fig. 3 where the object i8 is picked up by a lens 48, behind which are located four prisms 4|, 42, 43, 44, ad- Justed relative to the lens 40 and to each other so as to produce four images of the object. Associated with the prisms are color filters 45, 46, 41, 48. A second lens 49 projects the four color images i2, i3, l4, l5 on the screen l6.

In the modification of Fig. 4, mirrors are substituted for the prisms. Four images of the object iii are reflected by the mirrors 50, 5|, 52, 53, onto mirrors 64,55, 56, 51, which reflect the separate images through the color filters 45, 46, 41, 48, to the lens 48.

As previously explained, the quadchromatic lenses ii and 31 (Figs. 1 and 2) are substantially identical but are used oppositely.

The foregoing matter is disclosed in the above identified application.

I will now disclose a method and means for scanning which is particularly adaptable to the previously disclosed color television system, butwhlch has features useful in black and whitev television. For illustration, I have selected a scanning system which produces 525 lines in the color frame. That is, the picture produced on thescreen 38 (Fig. 2) would consist of 525 lines. This means that the beam 3| in producing the quadchromatic field comprising the images 33, 34, 35, 36, will be required to operate at 262 lines. Similarly, the screen i6 (Fig. 1) will be scanned with the same number of lines. As will presently be explained more in detail, thechoice of an odd number of lines in the frame results in an oddline interlace after the second scanning. A special means is then employed to shift the scanning grating one line vertically and to maintain it so displaced during the third and. fourth scanning cycles. An important result obtained by my invention is that each of the linesin the screen 38 goes through the complete cycle of four colors in the course of four scanning cycles. The result to be obtained is illustrated diagrammatically in Figs. 5, 6, '1 and 8. The color key is shown in Figure 9.

The first scan will produce a first color frame on the screen 38 (Fig. 2), the first four lines of which will be red, yellow, blue, green, in that order, as shown in Fig. 5. The second color field shown in Fig. 6 will have the first line blue, the second line green, the third line red, and the fourth line yellow, and so on through the four cycles, as illustrated in Figs. 5 to 8.

Fig. 10 illustrates ditically the quadchromatic field which comprises the four color images of the object, the red image may be in the first quadrant 6|, the blue imageinay be in ond line in the scan is the fifth line in the field.

The red and blue field of 6i and 62 are scanned in this manner until the beam reaches the yellow field 64, as indicated by the line 68. This first line in the yellow field is an even line in the color frame (see Fig. 5) where it is shown as being the second line. After the fiy-back the next line 69 traverses both the green field 63 and the yellow field 64. As shown in Fig. 5, the green line is the fourth line. It is to be noted at this point that in the first scanning odd lines in the fields 6| and 62 were scanned and even lines were scanned in the lower fields 63 and 64.

When the four images are colored by the quadchromatic lens 31 (Fig. 2), the color lines are optically interlaced, as illustrated in Fig. 5, so that the first line in Fig. 5 is a, red line taken from the field-6i (Fig. 10); the second line is a yellow line taken from'the field 64; the third line is a blue-line taken from the field 62; the fourth line is a green line taken from the field 63. It is to be noted that by arranging the images in a quadrangle and scanning the quadchromatic field the lines in each of the four fields are scanned in such a position that when the images are 0ptically superimposed an optical interlace results on account of the fact that all the lines scanned in the upper two fields are odd, whereas all the lines scanned in the lower two fields are even.

The result thus obtained I shall term seriate color line composition; that is, I compose the final color frame appearing on the screen 38 by arranging lines of diflerent color in consecutive order or in series, so that, in the first color frame produced, as illustrated in Fig. 5, the lines in numerical order are red, yellow, blue, green, red, yellow, etc. There are certain factors responsible for this result: producing a plurality of separate images of the object; arranging the images in such a way and scanning the group of images in such a way that when optically super-imposed the lines from the several images will be optically interlaced in proper order to produce a seriate color line composition.

After completely scanning the four fields 6|64 and after the vertical fiy-back, the first cycle concludes atthe end of 2625 lines. This means that the second scanning will begin at the upper left-hand corner 16 of the field 62, so that the first line in the second color frame will be blue, as shown in Fig. 6, and the third line will be red so that an odd-line interlace is automatically obtained by selecting an odd number of lines in the frame and in addition an automatic interchange of colors is obtained. Notice that in the first color frame (Fig. 5) the first line is red, whereas in the second color frame (Fig. 6) the first line is blue. Thus a second seriate color line composition is produced which differs from the first in order of colors. In order to bring the green and yellow into the first line in the last two scannings it is necessary to shift the scanning grating one line vertically. This is done, as will now be explained, by introducing a direct current pulse into the vertical deflection coils in order to move the grating of lines upwardly or downwardly whichever is desired.

Assuming that generator 24 of the vertical deflection coil 22 causes a standard saw-tooth curve 15, such as shown diagrammatically in Fig. 11, the result is obtained by super-imposing a pulse, such as that shown in Fig. 12 at 18, to alter the curve 15 to the shape shownat 11 in broken lines. Reviewing the operation so far by referring to Fig. 11, the first scanning of the quadchromatic fleld begins at the point 88. From 8| to 82 is the vertical fly-back time, and from the beginning 88, to the end 82 of the first scanning cycle is 262 lines. This causes an odd-line interlace during the second scanning from 82 to 83. During the fly-back time from 88 to 84 at the end of the second cycle the D. C. pulse 85 (Fig. 6) is introduced into the deflection coils so that the current is increased, as indicated bythe point 86 in the broken line curve 11 (Fig. 11) This, as pointed out above, causes vertical shift of the grating in order to pick up the even lines in fields 6| and 62 (Fig. and the odd lines in fields 63 and 84. At the end of the third cycle (point 81) on account of the fact that the cycle is 262 lines long, the fourth cycle will begin onehalf a line from the beginning of the third cycle.

The vertical shifting of the grating is efiected electronically as will now be described.

Referring to Fig. 1, atiming pulse generator 88 is supplied with a GO-cycle synchronizing pulse from the transmitter 25. The timing pulse generator 98 consists essentially of a conventional multivibrator circuit which generates a timing pulse of the frequency required to obtain the time interval shown in Fig. 12. In the present instance which has been chosen for illustration, this interval is one-fifteenth of a second because, as will be recalled, it is necessary to hold the grating displaced for two scanning cycles. Accordingly, a 7 /2 cycle timing pulse is required.

The output of the multivibrator circuit is illustrated by the curve 92 (Fig. 13). If necessary, the output of the multivibrator circuit may be amplified to obtain sharp cut-off, and reshaped, as indicated in broken lines at 93 and 94 in Fig. 13, by clipping off the tops of the curves.

The timing pulse generator is connected to the grid 95 of a tube 86 which has a negative cut-oil bias provided by the ba tery 91. The time constant of the coupling condenser 88 and resistor 88 is such as to pass the pulse to the said tube. The tube is connected to ground through a resistance I88 which is relatively small so as not to impair the normal operation of the deflection coil circuit. The power for the D. C. pulse is obtained from the battery IN.

The tube 96 (Fig. 1) merely acts as a switch to turn the current on and off through the tube and resistor I88. The coupling circuit, made up of the condenser 98 and the resister 89, is such as to pass the triggering pulse to the grid of tube 96. The bias voltage on the grid is set so that no current flows in the tube until the positive half of the pulse cycle reaches the grid. When this occurs maximum current flows through the tube producing a voltage across the resistance I88 for one-fifteenth of a second and so producing the required direct current pulse.

Since the amount of current required to shift the deflection field one scanning line is relatively small, the ohmic resistance of resister 88 may be or a small value with respect tothe ohmi impedance of the deflection coils. The amplitude of the current introduced into the deflection coils circuit is controlled by adjusting a slider tap on resistance I88. A second method would be to adiust the resistance as a whole to a value so that the right amplitude of pulse was produced. A third method is to vary the plate voltage and so control the maximum amount of current flowing through the tube and resistance I88. When a centering current is also required in the low frequency coil circuit there may be additional direct current flowing in the resistance I88 but the bias eflect of this may be counteracted by adjusting the bias voltage either in a positive or a negative direction as the case may be. The bias on the grid of tube 96 should always be great enough to keep it cut oil regardless of the scanning voltage and the exciting pulse on its grid should always be great enough that maximum current flows through the tube during its positive swing. This insures that the tube is only operating as a. switch and not as an amplifier. The voltage on tube 96 must be well regulated. The circuit could be adjusted to act as an amplifier but the regulation of the amplitude of the pulse is more diflicult. The direction of deflection which thispulse will give to the scanning field may be altered by connecting it in on one side or another of the grounding point of the scanning coils.

A similar means is employed in the receiver, as shown in Fig. 2. The transmitter sends out a sixty-cycle synchronous pulse which is received in the receiver and supplied to the timing pulse generator 98', which is similar to generator 98 employed in the transmitter. Likewise, the tube 86', with a condenser 98', is connected through a resistance 98' to a negative bias battery 91' and through a resistance I88 to ground. A battery I8l' supplies the power which is switched by the tube 96' into the deflection coil 38 to provide a D. C. pulse in synchronism with the D. C. pulse at the transmitter.

As a result, during the third scanning a third seriate color line composition is produced, as illustrated in Fig. 7, where the first line is green and the order of colors differs from that in the first and second (Figs. 5 and 6). At the conclusion of the third scanning the odd-line interlace effect changes the order of colors for the fourth scanning so that a fourth seriate color line composition is produced, as illustrated in Fig. 8 where the first line is yellow. At the end of the cycle of four scannings each line has gone through the cycle of four colors.

The system described above may be varied as to picture frequencies, interlace ratios, etc. Below is a table of difierent systems, the first of which is the one just described:

Table I System 1 2 3 4 5 Quadchromatic fields per For convenience, the above terms may be defined as follows:

Quadchromatic field-one scanning raster or the dot images;

Qfichromatic line-one scan line horizontally across adjacent images in a quadchromatic field;

Color field-one scanning raster of lines covering an image of one filter color;

Color frame-dour color fields of one quadchromatic field superimposed upon one another optically as at receiver; and

Frame-one full complement of lines .over an entire assembled picture area similar to that in black and white television.

For introducing the direct current pulse into an electrostatic system a circuit, similar .to that described above, is employed, as shown in Fig. 14. In this case the voltage across the resistance 2" is introduced into the deflection plates through coupling resister 203. Scanning voltage may be introduced into the deflection plates from an electrostatic generator (not shown) connected to leads at 204. I have shown a coupling resister 205 connected to a deflection plate and to a conventional centering potentiometer circuit 202 which may be connected to a D. C. voltage source (not shown). The desired polarity of field defiection may be obtained by introducing the pulse at the bottom sisters.

I claim:

1. The method of reproducing a picture of an object by television which comprises, producing a plurality of images of said object, arranging said images in a group, electronically scanning said group of images as a single picture with a single electron beam, transmitting the signals derived from said scanning, reproducing a group of images from said signals, and optically interlacing the lines of the reproduced images to produce a composite picture of the object.

2. The methodof reproducing a picture of an object by television in color which comprises, producing a plurality of images of said object in difierent colors, arranging said difierent color images in a group, electronically scanning said group of color images as a single picture with a single electron beam, transmitting the signals derived from said scanning, reproducing a group of images from said signals, restoring the colors to said images, and optically interlacing the color lines of the reproduced images to produce a seriate color line composition.

3. The method of reproducing a picture of an object by television in color which comprises, producing a plurality of images of said object in diflerent colors, arranging the difierent color images in a group, electronically scanning said group of color images as a single picture with a single electron beam, transmitting the signals derived from said scanning, reproducing a group of images from said signals, restoring the colors to said images, optically interlacing the color lines of the reproduced images to produce a seriate color line composition, and changing the sequence of scanning said diil'erent color images to efiect a change in the order of color lines in successive. seriate color line compositions.

4. The method of electronically scanning images of a fleld of view in a cathode ray tube which consists in scanning the field with a single electron beam. oyin an odd number of lines in the field to obtain geometrically an oddline interlace during two successive scanning cycles, shifting the scanning grating one line' from its original position beiore the beginning of either one of the coupling reor the third scanning cycle, maintaining the scanning rating in its shifted position during the third and fourth scanning-cycles, and shirting the scanning grating back to its origlnal position before the beginning oi the fifth scanning cycle, and repeating the scanning operation.

5. The method of televising an object in color which comprises, producing images in difierent colors of the object, disposing the color images side by side, scanning said color images as a single picture with a single electron beam, employing an odd number oi. lines in the field to obtain an odd line interlace, transmitting signals derived from said scanning, reproducing images from the trammitted signals, and forming a composite picture or the images reproduced.

6. A method ofv televising an object in color which comprises, optically producing i'our images of difierent color, arranging said images in a quadrangular field,- electronically scanning the field four times, beginning the first line in a different field each time, repeating the series of scannings cyclically, transmitting the signals derived from said scannings. reproducing tour images from the transmitted signals, and optically producing a composite picture from said four rebegins in the first color field, in the second scanning the first line begins in the second color field,

in the third scanning the second line begins in the first color field, in the fourth scanning the second line begins in the second color field, transmitting the signals derived from the scanning, reproducing four images from said signals, and forming a composite picture by combining said reproduced images.

8. In a television system, an electronic scanning device having horizontal and vertical deflection coils, means for controlling the flow of ourrent in said coils to cause a scanning operation, and means for cyclically introducing additional current in the vertical deflection coil to displace vertically the pattern of scanning lines on the field in order to scan lines left unscanned in the previous' scanning operation comprising means controlled by an alternating current circuit for electronically opening and closing a circuit containing a direct current source of power which is thereby periodically connected to the vertical deflection coil circuit. I

9. In a television system, an electronic scanning device having horizontal and vertical deflection coils, means for controlling the fiow of current in said coils to cause a scanning operation,

means for cyclicallyintroducing additional current in the vertical deflection coil to displace vertically the pattern or scanning lines on the field in order to scan lines left unscanned in the previous'scanning operation, comprising means controlled by an alternating current circuit for electronically opening and closing a circuit containing a direct current source of power which is thereby periodically connected to the vertical deflection coil circuit, an electronic reproducing device in the receiver having vertical and horizontal deflecting means responsive to signals derived from the transmitter, vertical deflection means including an alternating current circuit operable in synchronism with the corresponding circuit in the transmitter by means of synchronizing signals, and an electronic device for employing said alternating current circuit in the receiver to control the flow of direct current periodically into the vertical deflection coil in synchronism with the corresponding pulses of direct current in the deflection coil of the scanning device in the transmitter.

10. In a television system, an electronic scanning device having horizontal and vertical deflection coils, means for controlling the flow of current in said coils to cause a scanning operation, and means for cyclically introducing additional current in the vertical deflection coil to displace vertically the pattern of scanning lines on the field in order to scan lines left unscanned in the previous scanning operation, comprising means controlled by an alternating current circuit for electronically opening and closing a circuit containing a direct current source of power which is thereby periodically connected to the vertical deflection coil circuit, including an electron tube,

. and means to place a negative bias on the grid thereof to prevent operation of the tube during negative one-halt cycles of the alternating current.

11. The method of televising an object in color which comprises, optically producing four images of diflerent color, arranging said images in a quadrangular field, electronically scanning said field four times with a single electron beam, beginning the first line in the first image in the first scanning, employingan odd number of lines in the field so that in the second scanning the first line begins in the second image, shifting the scanning grating one line after the second scanning so that in the third scanning the first line begins in the third image, maintaining the grating in shifted position during the third and fourth scannings so that in the fourth scanning the first line begins in the fourth image, repeating the series of scanning cyclically, transmitting the signals derived from said scannin'gs, reproducing four images from the transmitted signals, restoring the color to said images, and optically interlacing the color lines of said reproduced images to produce a composite picture in color.

12. In a system employing an electronic scanning device having horizontal and vertical defleeting means, horizontal and vertical deflection generators, a circuit containing the horizontal generator and deflecting means, another circuit containing the vertical generator and deflecting means, and means controlled by an alternating current circuit for electronically connecting said vertical deflection circuit to a direct current source of power at predetermined time intervals to periodically displace the pattern of scanning lines vertica ly.

GEORGE E. SLEEPER, JR. 

